1. Technical Field
The invention relates to a device and a process for controlling a data transmission channel or data bus, particularly a data bus on which the data is serially transmitted according to a prescribed transmission protocol or bus protocol, as well as the use of a hierarchical processor architecture to control a data bus. The invention is particularly suited to the control of a number of field data buses or field buses for general applications and particularly for the control of field buses in vehicles.
2. Description of the Related Art
Data transmission channels or data buses are used for the transmission of data between electronic data processing installations, peripheral equipment, and the environment. This data transmission must be carried out according to certain rules, these being the transmission protocol or bus protocol. Due to development over time, a number of data buses have become established which permit data transmission according to the respective bus protocol specific to the data bus.
In data buses there are differences between bit serial data buses, where the data bits are transmitted singly and in sequence, and bit parallel data buses, where a certain number of data bits, one byte, is transmitted in parallel.
Amongst serial data buses, the field data bus or field bus has a special position. A field bus is a local communication network, in that it can replace point-to-point connections between one or more pickups and a data processing device, or between a data processing device and a display unit. The area of application of field buses is currently that of industrial production engineering. In addition, there are first applications using field buses in vehicles.
In the case of field buses, a number of bus variants have established themselves in the market, and which were conceived and optimized for a particular application. Normally, each of these bus variants has its own proprietary control, as the associated bus protocols are different.
In R. Prasad and J. D. Decotignie: "Field buses--The big bazaar, part 1: Problems in industrial communication", Bulletin of the Swiss Electrotechnical Association/Association of Swiss Power Stations, vol. 84, No. 21, Oct. 22nd, 1993, pages 11-17, a classification of field buses in the current world of communications, and the specific problems of using field buses were noted. They covered, for example, the control of a machine tool and the problem of cyclic or requested data exchange, the type of communication relationships and data characteristics, the period of validity and acknowledge time, and the complexity of process combinations. In addition, they covered the meaning of aspects of security and reliability when using field buses.
In R. Prasad and J. D. Decotignie: "Field buses--The big bazaar, part 2: The book of duties", Bulletin of the Swiss Electrotechnical Association/Association of Swiss Power Stations, vol. 84, No. 25, Dec. 17th, 1993, pages 26-30, the equipment characteristics and data for the design of a field bus were taken into consideration, topologies and transmission media were presented and a book of duties for field buses was drawn up. In this, the services of the application layer are included and the function of network administration determined.
In J. D. Decotignie: "Field buses--The big bazaar, part 3: Comparison with existing solutions", Bulletin of the Swiss Electrotechnical Association/Association of Swiss Power Stations, vol. 84, No. 21, Oct. 22nd, 1993, pages 27-34, different established field bus systems, such as BITBUS, CAN (controller area network), FIP (field instrumentation protocol), HART, INTERBUS-S, LON, MIL-STD-1553, SERCOS and PROFIBUS (German field bus standard DIN 19245) are presented and compared. It was concluded that currently numerous field bus variants exist but none of these variants can cover the whole spectrum of user requirements.
In W. Lawrenz: "AUTO BUSES for networking sensors/actuators, with examples from CAN", Automation Technology Practice, vol. 35, no. 8, August 1993, the protocol and the characteristics of an automotive field bus, the CAN (controller area network) field bus, were described in detail. Complete controls were presented for this, and for the circuit engineering components as well as for the program engineering components. In addition, different electrical circuits from several manufacturers were presented, which are necessary for the respective control of different automotive field buses.
Due to the different and in the main proprietary bus protocols of individual data buses, currently a specific control is required for each data bus. Together with the number of data bus variants currently established on the market, there is also a large number of data bus controls which can only be used for one respective type of bus.
This means high costs for the manufacturer of data bus controls, as the scales of manufacture are small due to the very limited applications. For the user of data bus controls, the number of data bus controls means high costs due to the supply of several data bus controls required in order to be able to work with the different data buses.
In addition, adapting a new data bus type and its data bus protocol requires a change in the circuit engineering of existing data bus controls, particularly an expansion or modification of individual circuit engineering functions of the data bus control, and thus increased requirements in development, time and costs.